1. Field of the Invention
This invention relates to coating applicators, such as for the application of polish to shoes. The applicator has a shape retentive open pore wicking pad for controllably transferring fluid coating material to the surface of an object to be coated. Because of the relative stability of the pad, small or narrow areas can be coated even though they are adjacent areas that are not to be coated or that are of different colors.
2. Description of Related Art
Present coating applicators, such as shoe polish applicators, are designed for the care of shoes that are of one color. They are designed to yield so that curved surfaces and hard to reach areas can be contacted by the readily deformable wicking pad. The applicator of the patent issued 15 Sep. 1964 to J. R. Gilchrist et al., U.S. Pat. No. 3,148,401, is representative of the type that have a soft, readily deformable foam or fabric pad for wicking the liquid polish from a supply container and spreading the polish onto a surface such as a shoe. The pads are generally made of a polyurethane or other sponge with a large open cell configuration or of a felt material. When pressed against a shoe to release the polish, the pad surface engages the shoe and deforms so that its shape and dimensions are significantly altered to conform to the shape of the surface area being coated.
A problem with liquid applicators using soft foam wicking application pads is that the compacted foam often becomes so thin that its wicking characteristics are significantly altered; the compressed foam often becomes permanently compacted; and as the liquid of the polish dries and solidifies in the pad, the pad becomes a hardened mass that is incapable of conforming to the contours of the shoe. Frequently, on hardening, the pad clogs and will no longer permit the passage of the coating material or polish. Another problem is that soft foam is prone to being worn or scraped off during use. This usually results in an uneven application or puddling of the coating on the surface. When multi-color shoes or other surfaces with irregular patterns are coated, adjacent surface areas are routinely inadvertently coated also.
U.S. Pat. No. 4,925,327, issued 15 May 1990 to D. Wirt, teaches a liquid applicator with a supply and open cell elastomer foam sponge. The foam is given a permanent compression set with a reduction in its original volume of from 1.5 to 10. A reduction in volume of 1/2 to 1/4 its original volume is preferred. The sponge has from 10 to 100 pores per linear inch with 90 pores per inch preferred. A layer of porous unfoamed material is used to meter the liquid from the supply to the sponge applicator. The combination is designed or selected so that the liquid will wet but not drip, the storage capacity (density) of the sponge will be regulated to hold the amount of liquid to be dispensed, and to control or adjust the viscosity and the surface tension of the liquid to be dispensed.
The standard open cell pad, such as used by KIWI.sub..TM. and Gilchrist et al (U.S. Pat. No. 3,248,401), have a coating surface area of essentially 5 cm.sup.2 and a thickness of essentially 3/4 cm. A pressure of 2,000 gms applied uniformly over the 5 cm.sup.2 surface area will compress this standard foam pad to about 1/2 its original thickness. Using the common type foam applicator, a pressure of up to 19 grams on a corner of the pad produces a line of 3 mm, and 23 to 25 grams produces a line of 5 mm, and 140 to 155 gms produces a line of 15 mm in width. The slit valve is normally opened with a force of between 2,500 to 3,200 gms on the applicator.
There has been a general assumption that large pores were necessary to conduct the coating, and in particular a pigment containing coating material, through a porous applicator pad. Even with the use of large pores, there has been a problem with the pads hardening and preventing the free flow of the coating material through the pad.